This project will implement an initial phase of California-2100 (Cal21),
which is aimed at making and evaluating high resolution estimates of climate
change over California out to the year 2100. Emphasis in this initial WRC
component of this project will be given to evaluating how well regional climate
models reproduce the interannual variations of important components of the
water budget for California, utilizing both observations and global climate
model (GCM) output as the regional model input.

The overall goals of Cal21 are to provide:
1. Assessments of the quality of global climate models in recreating recent
past climates. The comparison data will be primarily the global NCEP Global
Reanalysis (NGR) and long-term satellite data sets. Included will be a
careful determination of the biases in the climate models relative to observations.
These assessments will serve as one measure of the likely quality of forecasts
by these models of future climates.
2. Comparisons for recent past climates of the ability of various regional
models to transform lower resolution global observational analyses and global
climate model output (with possible bias adjustments) to higher resolution
regional scale output. The comparison data will be the NCEP Regional Reanalysis
(NRR) observations and other high quality regional scale gridded data sets.
These comparisons will assess by the ability of the climate models, which
necessarily have biases and other errors with respect to the global reanalyses,
to reproduce high resolution observations of recent climate.
3. Production of high resolution forecasts of future California climates,
which have objective measures of uncertainty and confidence based upon the
output of the best available GCMs and the best quality regional model downscaling.

This WRC proposal is designed to demonstrate the utility of a major component
of Cal21 by showing that regional scale climate models can be used to accurately
downscale temperature, precipitation and evaporation from course grid observational
analyses and climate model output to higher resolution output. Emphasis will
be given to analyzing those variables which are important for future water
management in California. An important product of this work will be statewide
high resolution maps of major climatic variables along with objective assessments
of the uncertainties.